The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform
Eckhard Boles - One of the best experts on this subject based on the ideXlab platform.
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An engineered fatty acid synthase combined with a carboxylic acid reductase enables de novo production of 1-Octanol in Saccharomyces cerevisiae
Biotechnology for Biofuels, 2018Co-Authors: Sandra Henritzi, Martin Grininger, Manuel Fischer, Mislav Oreb, Eckhard BolesAbstract:BackgroundThe ideal biofuel should not only be a regenerative fuel from renewable feedstocks, but should also be compatible with the existing fuel distribution infrastructure and with normal car engines. As the so-called drop-in biofuel, the fatty alcohol 1-Octanol has been described as a valuable substitute for diesel and jet fuels and has already been produced fermentatively from sugars in small amounts with engineered bacteria via reduction of thioesterase-mediated premature release of octanoic acid from fatty acid synthase or via a reversal of the β-oxidation pathway.ResultsThe previously engineered short-chain acyl-CoA producing yeast Fas1R1834K/Fas2 fatty acid synthase variant was expressed together with carboxylic acid reductase from Mycobacterium marinum and phosphopantetheinyl transferase Sfp from Bacillus subtilis in a Saccharomyces cerevisiae Δfas1 Δfas2 Δfaa2 mutant strain. With the involvement of endogenous thioesterases, alcohol dehydrogenases, and aldehyde reductases, the synthesized octanoyl-CoA was converted to 1-Octanol up to a titer of 26.0 mg L−1 in a 72-h fermentation. The additional accumulation of 90 mg L−1 octanoic acid in the medium indicated a bottleneck in 1-Octanol production. When octanoic acid was supplied externally to the yeast cells, it could be efficiently converted to 1-Octanol indicating that re-uptake of octanoic acid across the plasma membrane is not limiting. Additional overexpression of aldehyde reductase Ahr from Escherichia coli nearly completely prevented accumulation of octanoic acid and increased 1-Octanol titers up to 49.5 mg L−1. However, in growth tests concentrations even lower than 50.0 mg L−1 turned out to be inhibitory to yeast growth. In situ extraction in a two-phase fermentation with dodecane as second phase did not improve growth, indicating that 1-Octanol acts inhibitive before secretion. Furthermore, 1-Octanol production was even reduced, which results from extraction of the intermediate octanoic acid to the organic phase, preventing its re-uptake.ConclusionsBy providing chain length control via an engineered octanoyl-CoA producing fatty acid synthase, we were able to specifically produce 1-Octanol with S. cerevisiae. Before metabolic engineering can be used to further increase product titers and yields, strategies must be developed that cope with the toxic effects of 1-Octanol on the yeast cells.
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An engineered fatty acid synthase combined with a carboxylic acid reductase enables de novo production of 1-Octanol in Saccharomyces cerevisiae.
Biotechnology for biofuels, 2018Co-Authors: Sandra Henritzi, Martin Grininger, Manuel Fischer, Mislav Oreb, Eckhard BolesAbstract:The ideal biofuel should not only be a regenerative fuel from renewable feedstocks, but should also be compatible with the existing fuel distribution infrastructure and with normal car engines. As the so-called drop-in biofuel, the fatty alcohol 1-Octanol has been described as a valuable substitute for diesel and jet fuels and has already been produced fermentatively from sugars in small amounts with engineered bacteria via reduction of thioesterase-mediated premature release of octanoic acid from fatty acid synthase or via a reversal of the β-oxidation pathway. The previously engineered short-chain acyl-CoA producing yeast Fas1R1834K/Fas2 fatty acid synthase variant was expressed together with carboxylic acid reductase from Mycobacterium marinum and phosphopantetheinyl transferase Sfp from Bacillus subtilis in a Saccharomyces cerevisiae Δfas1 Δfas2 Δfaa2 mutant strain. With the involvement of endogenous thioesterases, alcohol dehydrogenases, and aldehyde reductases, the synthesized octanoyl-CoA was converted to 1-Octanol up to a titer of 26.0 mg L-1 in a 72-h fermentation. The additional accumulation of 90 mg L-1 octanoic acid in the medium indicated a bottleneck in 1-Octanol production. When octanoic acid was supplied externally to the yeast cells, it could be efficiently converted to 1-Octanol indicating that re-uptake of octanoic acid across the plasma membrane is not limiting. Additional overexpression of aldehyde reductase Ahr from Escherichia coli nearly completely prevented accumulation of octanoic acid and increased 1-Octanol titers up to 49.5 mg L-1. However, in growth tests concentrations even lower than 50.0 mg L-1 turned out to be inhibitory to yeast growth. In situ extraction in a two-phase fermentation with dodecane as second phase did not improve growth, indicating that 1-Octanol acts inhibitive before secretion. Furthermore, 1-Octanol production was even reduced, which results from extraction of the intermediate octanoic acid to the organic phase, preventing its re-uptake. By providing chain length control via an engineered octanoyl-CoA producing fatty acid synthase, we were able to specifically produce 1-Octanol with S. cerevisiae. Before metabolic engineering can be used to further increase product titers and yields, strategies must be developed that cope with the toxic effects of 1-Octanol on the yeast cells.
Richard G. Compton - One of the best experts on this subject based on the ideXlab platform.
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Sonoelectrochemically modified electrodes: Ultrasound assisted electrode cleaning, conditioning, and product trapping in 1-Octanol/water emulsion systems
Electrochimica Acta, 1998Co-Authors: Frank Marken, Richard G. ComptonAbstract:Abstract Electrode processes for three types of water soluble redox systems in the presence of power ultrasound have been studied in a non-conventional environment: the 1-Octanol/water microemulsion. The capability of ultrasound both to emulsify instantly a liquid/liquid system in the absence of stabilizing agents and to generate a high flux of material towards the electrode surface is shown to provide new tools for the control of electrochemical redox processes. First, the electrochemical reduction of Ru(NH 3 ) 3+ 6 has been studied. This is known to be a fast and reversible process at a glassy carbon electrode in aqueous 0.1 M KCl even in the presence of ultrasound. The addition of 1-Octanol does not significantly affect this redox process up to a very high 1-Octanol content in the emulsion system, although a thin film or adsorbed layer of 1-Octanol is believed to be present at the electrode surface. Surprisingly, the limiting current and voltammetric characteristics of the reduction process remain nearly unaffected, until, at a critical ratio of ca . 50 vol% 1-Octanol, the voltammetric response suddenly disappears, attributed to loss of conductivity in the bulk liquid. Second, and in contrast, the reduction and deposition of Pb 2+ from aqueous 0.1 M HClO 4 at a glassy carbon electrode is strongly affected even by small quantities of 1-Octanol, again consistent with a thin layer of 1-Octanol being permanently present at the electrode/emulsion interface. With increasing quantities of added 1-Octanol the reduction process is gradually shifted several hundred mV to more negative potentials whereas the anodic lead stripping response is first shifted to more positive potentials and finally disappears. Third, the reduction of cobalticinium, CoCp + 2 (Cp= η 5 −C 5 H 5 ), in aqueous 0.1 M KOH under silent conditions results in the formation of nearly insoluble, neutral cobaltocene which precipitates at the glassy carbon electrode surface. In the presence of 1-Octanol the neutral product dissolves in the organic liquid and allows voltammetric experiments to be conducted without loss of electrode activity due to blocking. The efficiency and the mechanism of this product ‘trapping’ process in the presence of 1-Octanol is discussed.
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Sonoelectrochemically modified electrodes: ultrasound assisted electrode cleaning, conditioning, and product trapping in 1-Octanol/water emulsion systems
Electrochimica Acta, 1998Co-Authors: Frank Marken, Richard G. ComptonAbstract:Electrode processes for three types of water soluble redox systems in the presence of power ultrasound have been studied in a non-conventional environment: the 1-Octanol/water microemulsion. The capability of ultrasound both to emulsify instantly a liquid/liquid system in the absence of stabilizing agents and to generate a high flux of material towards the electrode surface is shown to provide new tools for the control of electrochemical redox processes. First, the electrochemical reduction of Ru(NH3)63+ has been studied. This is known to be a fast and reversible process at a glassy carbon electrode in aqueous 0.1 M KCl even in the presence of ultrasound. The addition of 1-Octanol does not significantly affect this redox process up to a very high 1-Octanol content in the emulsion system, although a thin film or adsorbed layer of 1-Octanol is believed to be present at the electrode surface. Surprisingly, the limiting current and voltammetric characteristics of the reduction process remain nearly unaffected, until, at a critical ratio of ca. 50 vol% 1-Octanol, the voltammetric response suddenly disappears, attributed to loss of conductivity in the bulk liquid. Second, and in contrast, the reduction and deposition of Pb2+ from aqueous 0.1 M HClO4 at a glassy carbon electrode is strongly affected even by small quantities of 1-Octanol, again consistent with a thin layer of 1-Octanol being permanently present at the electrode/emulsion interface. With increasing quantities of added 1-Octanol the reduction process is gradually shifted several hundred mV to more negative potentials whereas the anodic lead stripping response is first shifted to more positive potentials and finally disappears. Third, the reduction of cobalticinium, CoCp2+ (Cp = η5-C5H5), in aqueous 0.1 M KOH under silent conditions results in the formation of nearly insoluble, neutral cobaltocene which precipitates at the glassy carbon electrode surface. In the presence of 1-Octanol the neutral product dissolves in the organic liquid and allows voltammetric experiments to be conducted without loss of electrode activity due to blocking. The efficiency and the mechanism of this product 'trapping' process in the presence of 1-Octanol is discussed. © 1998 Elsevier Science Ltd. All rights reserved
Sandra Henritzi - One of the best experts on this subject based on the ideXlab platform.
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An engineered fatty acid synthase combined with a carboxylic acid reductase enables de novo production of 1-Octanol in Saccharomyces cerevisiae
Biotechnology for Biofuels, 2018Co-Authors: Sandra Henritzi, Martin Grininger, Manuel Fischer, Mislav Oreb, Eckhard BolesAbstract:BackgroundThe ideal biofuel should not only be a regenerative fuel from renewable feedstocks, but should also be compatible with the existing fuel distribution infrastructure and with normal car engines. As the so-called drop-in biofuel, the fatty alcohol 1-Octanol has been described as a valuable substitute for diesel and jet fuels and has already been produced fermentatively from sugars in small amounts with engineered bacteria via reduction of thioesterase-mediated premature release of octanoic acid from fatty acid synthase or via a reversal of the β-oxidation pathway.ResultsThe previously engineered short-chain acyl-CoA producing yeast Fas1R1834K/Fas2 fatty acid synthase variant was expressed together with carboxylic acid reductase from Mycobacterium marinum and phosphopantetheinyl transferase Sfp from Bacillus subtilis in a Saccharomyces cerevisiae Δfas1 Δfas2 Δfaa2 mutant strain. With the involvement of endogenous thioesterases, alcohol dehydrogenases, and aldehyde reductases, the synthesized octanoyl-CoA was converted to 1-Octanol up to a titer of 26.0 mg L−1 in a 72-h fermentation. The additional accumulation of 90 mg L−1 octanoic acid in the medium indicated a bottleneck in 1-Octanol production. When octanoic acid was supplied externally to the yeast cells, it could be efficiently converted to 1-Octanol indicating that re-uptake of octanoic acid across the plasma membrane is not limiting. Additional overexpression of aldehyde reductase Ahr from Escherichia coli nearly completely prevented accumulation of octanoic acid and increased 1-Octanol titers up to 49.5 mg L−1. However, in growth tests concentrations even lower than 50.0 mg L−1 turned out to be inhibitory to yeast growth. In situ extraction in a two-phase fermentation with dodecane as second phase did not improve growth, indicating that 1-Octanol acts inhibitive before secretion. Furthermore, 1-Octanol production was even reduced, which results from extraction of the intermediate octanoic acid to the organic phase, preventing its re-uptake.ConclusionsBy providing chain length control via an engineered octanoyl-CoA producing fatty acid synthase, we were able to specifically produce 1-Octanol with S. cerevisiae. Before metabolic engineering can be used to further increase product titers and yields, strategies must be developed that cope with the toxic effects of 1-Octanol on the yeast cells.
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An engineered fatty acid synthase combined with a carboxylic acid reductase enables de novo production of 1-Octanol in Saccharomyces cerevisiae.
Biotechnology for biofuels, 2018Co-Authors: Sandra Henritzi, Martin Grininger, Manuel Fischer, Mislav Oreb, Eckhard BolesAbstract:The ideal biofuel should not only be a regenerative fuel from renewable feedstocks, but should also be compatible with the existing fuel distribution infrastructure and with normal car engines. As the so-called drop-in biofuel, the fatty alcohol 1-Octanol has been described as a valuable substitute for diesel and jet fuels and has already been produced fermentatively from sugars in small amounts with engineered bacteria via reduction of thioesterase-mediated premature release of octanoic acid from fatty acid synthase or via a reversal of the β-oxidation pathway. The previously engineered short-chain acyl-CoA producing yeast Fas1R1834K/Fas2 fatty acid synthase variant was expressed together with carboxylic acid reductase from Mycobacterium marinum and phosphopantetheinyl transferase Sfp from Bacillus subtilis in a Saccharomyces cerevisiae Δfas1 Δfas2 Δfaa2 mutant strain. With the involvement of endogenous thioesterases, alcohol dehydrogenases, and aldehyde reductases, the synthesized octanoyl-CoA was converted to 1-Octanol up to a titer of 26.0 mg L-1 in a 72-h fermentation. The additional accumulation of 90 mg L-1 octanoic acid in the medium indicated a bottleneck in 1-Octanol production. When octanoic acid was supplied externally to the yeast cells, it could be efficiently converted to 1-Octanol indicating that re-uptake of octanoic acid across the plasma membrane is not limiting. Additional overexpression of aldehyde reductase Ahr from Escherichia coli nearly completely prevented accumulation of octanoic acid and increased 1-Octanol titers up to 49.5 mg L-1. However, in growth tests concentrations even lower than 50.0 mg L-1 turned out to be inhibitory to yeast growth. In situ extraction in a two-phase fermentation with dodecane as second phase did not improve growth, indicating that 1-Octanol acts inhibitive before secretion. Furthermore, 1-Octanol production was even reduced, which results from extraction of the intermediate octanoic acid to the organic phase, preventing its re-uptake. By providing chain length control via an engineered octanoyl-CoA producing fatty acid synthase, we were able to specifically produce 1-Octanol with S. cerevisiae. Before metabolic engineering can be used to further increase product titers and yields, strategies must be developed that cope with the toxic effects of 1-Octanol on the yeast cells.
Frank Marken - One of the best experts on this subject based on the ideXlab platform.
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Sonoelectrochemically modified electrodes: Ultrasound assisted electrode cleaning, conditioning, and product trapping in 1-Octanol/water emulsion systems
Electrochimica Acta, 1998Co-Authors: Frank Marken, Richard G. ComptonAbstract:Abstract Electrode processes for three types of water soluble redox systems in the presence of power ultrasound have been studied in a non-conventional environment: the 1-Octanol/water microemulsion. The capability of ultrasound both to emulsify instantly a liquid/liquid system in the absence of stabilizing agents and to generate a high flux of material towards the electrode surface is shown to provide new tools for the control of electrochemical redox processes. First, the electrochemical reduction of Ru(NH 3 ) 3+ 6 has been studied. This is known to be a fast and reversible process at a glassy carbon electrode in aqueous 0.1 M KCl even in the presence of ultrasound. The addition of 1-Octanol does not significantly affect this redox process up to a very high 1-Octanol content in the emulsion system, although a thin film or adsorbed layer of 1-Octanol is believed to be present at the electrode surface. Surprisingly, the limiting current and voltammetric characteristics of the reduction process remain nearly unaffected, until, at a critical ratio of ca . 50 vol% 1-Octanol, the voltammetric response suddenly disappears, attributed to loss of conductivity in the bulk liquid. Second, and in contrast, the reduction and deposition of Pb 2+ from aqueous 0.1 M HClO 4 at a glassy carbon electrode is strongly affected even by small quantities of 1-Octanol, again consistent with a thin layer of 1-Octanol being permanently present at the electrode/emulsion interface. With increasing quantities of added 1-Octanol the reduction process is gradually shifted several hundred mV to more negative potentials whereas the anodic lead stripping response is first shifted to more positive potentials and finally disappears. Third, the reduction of cobalticinium, CoCp + 2 (Cp= η 5 −C 5 H 5 ), in aqueous 0.1 M KOH under silent conditions results in the formation of nearly insoluble, neutral cobaltocene which precipitates at the glassy carbon electrode surface. In the presence of 1-Octanol the neutral product dissolves in the organic liquid and allows voltammetric experiments to be conducted without loss of electrode activity due to blocking. The efficiency and the mechanism of this product ‘trapping’ process in the presence of 1-Octanol is discussed.
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Sonoelectrochemically modified electrodes: ultrasound assisted electrode cleaning, conditioning, and product trapping in 1-Octanol/water emulsion systems
Electrochimica Acta, 1998Co-Authors: Frank Marken, Richard G. ComptonAbstract:Electrode processes for three types of water soluble redox systems in the presence of power ultrasound have been studied in a non-conventional environment: the 1-Octanol/water microemulsion. The capability of ultrasound both to emulsify instantly a liquid/liquid system in the absence of stabilizing agents and to generate a high flux of material towards the electrode surface is shown to provide new tools for the control of electrochemical redox processes. First, the electrochemical reduction of Ru(NH3)63+ has been studied. This is known to be a fast and reversible process at a glassy carbon electrode in aqueous 0.1 M KCl even in the presence of ultrasound. The addition of 1-Octanol does not significantly affect this redox process up to a very high 1-Octanol content in the emulsion system, although a thin film or adsorbed layer of 1-Octanol is believed to be present at the electrode surface. Surprisingly, the limiting current and voltammetric characteristics of the reduction process remain nearly unaffected, until, at a critical ratio of ca. 50 vol% 1-Octanol, the voltammetric response suddenly disappears, attributed to loss of conductivity in the bulk liquid. Second, and in contrast, the reduction and deposition of Pb2+ from aqueous 0.1 M HClO4 at a glassy carbon electrode is strongly affected even by small quantities of 1-Octanol, again consistent with a thin layer of 1-Octanol being permanently present at the electrode/emulsion interface. With increasing quantities of added 1-Octanol the reduction process is gradually shifted several hundred mV to more negative potentials whereas the anodic lead stripping response is first shifted to more positive potentials and finally disappears. Third, the reduction of cobalticinium, CoCp2+ (Cp = η5-C5H5), in aqueous 0.1 M KOH under silent conditions results in the formation of nearly insoluble, neutral cobaltocene which precipitates at the glassy carbon electrode surface. In the presence of 1-Octanol the neutral product dissolves in the organic liquid and allows voltammetric experiments to be conducted without loss of electrode activity due to blocking. The efficiency and the mechanism of this product 'trapping' process in the presence of 1-Octanol is discussed. © 1998 Elsevier Science Ltd. All rights reserved
Rodney Croteau - One of the best experts on this subject based on the ideXlab platform.
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Evidence for an Elongation/Reduction/C1-Elimination Pathway in the Biosynthesis of n-Heptane in Xylem of Jeffrey Pine
Plant physiology, 1996Co-Authors: Thomas J. Savage, Marta K. Hristova, Rodney CroteauAbstract:The biosynthetic pathway to n-heptane was investigated by examining the effect of the [beta]-keto acyl-acyl carrier protein synthase inhibitor (2R,3S)-2,3-epoxy-4-oxo-7E,10E-dodecadienamide (cerulenin), a thiol reagent ([beta]-mercaptoethanol), and an aldehydetrapping reagent (hydroxylamine) on the biosynthesis of n-[14C]heptane and putative intermediates in xylem sections of Jeffrey pine (Pinus jeffreyi Grev. & Balf.) incubated with [14C]acetate. Cerulenin inhibited C18 fatty acid biosynthesis but had relatively little effect on radiolabel incorporation into C8 fatty acyl groups and n-heptane. [beta]-Mercaptoethanol inhibited n-heptane biosynthesis, with a corresponding accumulation of radiolabel into both octanal and 1-Octanol, whereas hydroxylamine inhibited both n-heptane and 1-Octanol biosynthesis, with radiolabel accumulation in octyl oximes. [14C]Octanal was converted to both n-heptane and 1-Octanol when incubated with xylem sections, whereas [14C]1-Octanol was converted to octanal and n-heptane in a hydroxylamine-sensitive reaction. These results suggest a pathway for the biosynthesis of n-heptane whereby acetate is polymerized via a typical fatty acid synthase reaction sequence to yield a C8 thioester, which subsequently undergoes a two-electron reduction to generate a free thiol and octanal, the latter of which alternately undergoes an additional, reversible reduction to form 1-Octanol or loss of C1 to generate n-heptane.
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evidence for an elongation reduction c1 elimination pathway in the biosynthesis of n heptane in xylem of jeffrey pine
Plant Physiology, 1996Co-Authors: Thomas J. Savage, Marta K. Hristova, Rodney CroteauAbstract:The biosynthetic pathway to n-heptane was investigated by examining the effect of the [beta]-keto acyl-acyl carrier protein synthase inhibitor (2R,3S)-2,3-epoxy-4-oxo-7E,10E-dodecadienamide (cerulenin), a thiol reagent ([beta]-mercaptoethanol), and an aldehydetrapping reagent (hydroxylamine) on the biosynthesis of n-[14C]heptane and putative intermediates in xylem sections of Jeffrey pine (Pinus jeffreyi Grev. & Balf.) incubated with [14C]acetate. Cerulenin inhibited C18 fatty acid biosynthesis but had relatively little effect on radiolabel incorporation into C8 fatty acyl groups and n-heptane. [beta]-Mercaptoethanol inhibited n-heptane biosynthesis, with a corresponding accumulation of radiolabel into both octanal and 1-Octanol, whereas hydroxylamine inhibited both n-heptane and 1-Octanol biosynthesis, with radiolabel accumulation in octyl oximes. [14C]Octanal was converted to both n-heptane and 1-Octanol when incubated with xylem sections, whereas [14C]1-Octanol was converted to octanal and n-heptane in a hydroxylamine-sensitive reaction. These results suggest a pathway for the biosynthesis of n-heptane whereby acetate is polymerized via a typical fatty acid synthase reaction sequence to yield a C8 thioester, which subsequently undergoes a two-electron reduction to generate a free thiol and octanal, the latter of which alternately undergoes an additional, reversible reduction to form 1-Octanol or loss of C1 to generate n-heptane.
